#include <stdio.h>

#define exchange(a, b) {int t; t=a; a=b; b=t;}

/**
 * 题目：宏#define命令练习2。
*/
int main(int argc, char const *argv[])
{
    int x = 10;
    int y = 20;
    printf("x=%d, y=%d\n", x, y);
    exchange(x, y);
    printf("x=%d, y=%d\n", x, y);

    return 0;
}